Sacroiliac (SI) joint region pain explored in AHT research

The prevalence and characteristics of sacroiliac (SI) joint region pain and its relationship to lameness in horses has been investigated in pioneering research conducted at the Animal Health Trust, one of the UK’s leading veterinary charities.

The research, conducted by Dr Sue Dyson, Head of Clinical Orthopaedics at the AHT and Amy Barstow, a previous AHT intern, built on previous AHT research that recognised SI joint region pain as a contributor to poor performance and/or hindlimb lameness. As the first large-scale study of its kind, the research provides important guidance for both vets and horse owners on the clinical signs of SI joint region pain and how best to examine it.

Notable results include the observation that clinical signs of SI joint region pain are worse when horses are ridden, such as bucking in canter and spontaneously breaking from canter. This highlights the importance of vets examining horses under saddle wherever possible in order to observe the true severity and breadth of the clinical signs.

Clinical signs of SI joint region pain can be dramatically reduced following diagnostic analgesia, a safe but non-specific block. Signs suggestive of SI joint region pain included canter quality that is worse than trot, and bucking and kicking out especially in canter. Bunny-hopping type canter, being on the forehand and croup high or a stiff, stilted canter, changing legs behind, spontaneously breaking from canter to trot and being reluctant to canter were also commonly observed, as well as the tendency to come above the bit. For horses showing the above signs, blocking the SI joint in a diagnostic investigation could provide crucial answers.

The research also found that only 42% of horses which had a positive response to SI block and underwent nuclear scintigraphy had abnormal radiopharmaceutical uptake (RU), showing that scintigraphy alone is unreliable for the diagnosis of SI joint pain. However, the use of ultrasonography and scintigraphy in conjunction with an SI block can provide additional information in some horses.

The majority of horses in the study had SI joint region pain and hindlimb lameness. Although clear improvement in lameness in hand was seen in some horses after removing the source of pain in the lame limb, ridden exercise highlighted the persistence of another source of pain, which was sometimes worse after abolishing the lameness. This again emphasises the crucial importance of ridden exercise in both trot and canter when assessing lameness and poor performance.

Dr Sue Dyson said, “Assessing the effect of treatment of the SI joints is not an effective method of diagnosis; the use of nerve blocks is much more reliable.”

The Animal Health Trust’s Equine Clinic is experienced in diagnosing and treating SI joint region pain in horses and offers a fully comprehensive referral service. If you are concerned that your horse is showing signs suggestive of SI joint region pain, speak to your vet and ask for a referral.

The Animal Health Trust is a veterinary charity, based in Suffolk, which offers clinical referral services and diagnostic testing for horses, dogs and cats in East Anglia, across the UK and internationally. Through its research programmes it develops new diagnostic tests, treatments and vaccines to help thousands of animals.